1. Field of the Invention
The present invention relates to an endoscope apparatus that has a function that adjusts the brightness of an endoscope image, and a control method for the endoscope apparatus.
2. Description of the Related Art
In order to photograph a dark inside of a body cavity and obtain an endoscope image with proper brightness, an endoscope apparatus illuminates the inside of the body cavity with an illuminating light that has an automatic light adjustment function and performs brightness adjustment processing with respect to an image that is picked up. As the automatic light adjustment function, a diaphragm of a light source apparatus is controlled to adjust an amount of light in accordance with the brightness of the endoscope image that is calculated by a photometry portion that calculates the brightness of an object.
In Japanese Patent Application Laid-Open Publication No. 2001-154232 and Japanese Patent Application Laid-Open Publication No. 2004-267290, the applicants disclose an electronic endoscope apparatus and the like that adopts a mean photometric method that is based on a mean value of brightness with respect to a part that corresponds to a periphery part in an image pickup range and adopts a peak photometric method that is based on a peak value of brightness for a center part in the image pickup range to thereby enable observation with the optimal brightness. Compared to a photometric method that is based on a mean value of the brightness of an entire screen, according to this photometric method more appropriate brightness control can be performed when observing a gastric angle part or the like that contains a region of interest of a user at a center region.
When observing a lumen-shaped object such as the large intestine or the esophagus, there are many cases in which there is a lumen on a deep side in a center region of the image and there is a luminal wall at a peripheral region of the image. Because the lumen on the deep side is far from the distal end portion of the endoscope in which an illumination portion is disposed, the lumen on the deep side is dark. In contrast, the luminal wall that has the region of interest of the user is near to the distal end portion of the endoscope, and is therefore bright. When using an endoscope apparatus that measures brightness and adjusts the light amount by taking the entire region of an endoscope image as an object, a luminal wall at a peripheral region of the endoscope image becomes too bright. Consequently, it has been necessary for the user to perform an operation to bend the distal end portion so that the region of interest becomes the center region of the endoscope image.